unknown problem with my file, not possible to 3dprint in DXF or STL
Not watertight mesh

One thing that may prevent a mesh from being printed, as you already pointed out, is the presence of "holes", which sholud be intended as parts of the mesh that create a discontinuity in the surface.

If you run the Select Boundary loop operator on the mesh:



You'll see that two main edge loops are not connected:



All the rideged surface on the top it's on its own. Being close to each other is not sufficient, you must join the two edgeloops.



A quick and dirty workaround could be to use the new Voxel Remesher tool to fix all the topology issues.

With a low cell size (something like 0.003 for example) you should be able to get an almost identical mesh.